Flask



FIG. 1 is a top plan view of the flask;

FIG. 2 is a bottom plan view of the flask;

FIG. 3 is a front elevation of the flask;

FIG. 4 is a left side elevation of the flask;

FIG. 5 is a rear elevation of the flask; and,

FIG. 6 is a right side elevation of the flask. 

The ornamental design for a flask, as shown and described. 